Mitochondria Transfer to CD4+ T Cells May Alleviate Rheumatoid Arthritis by Suppressing Pro-Inflammatory Cytokine Production

Abstract

CD4⁺ T cells contribute to the pathogenesis of autoimmune diseases such as rheumatoid arthritis (RA). These cells infiltrate the joints of RA patients and produce cytokines, including Tumor necrosis factor (TNF)-α, that drive joint inflammation and bone destruction. Although biologic therapeutics targeting T cells and TNF-α have benefited patients suffering from RA, some patients are refractory to these therapies, develop antibodies that neutralize these biologics, or develop undesirable side effects. Recent studies indicate that CD4⁺ T cell cytokine production is regulated in part by specific metabolic modules, suggesting that immunometabolic pathways could represent a novel therapeutic strategy for T cell-mediated diseases such as RA. Wu et al. (2021) demonstrate that mitochondrial function is impaired in CD4⁺ T cells from RA patients, leading to reduced levels of various citric acid cycle metabolites (e.g., aspartate) that regulate TNF-α production. Treatment of RA-associated T cells with purified mitochondria was sufficient to restore these metabolic defects, limit production of numerous pro-inflammatory cytokines such as TNF-α and IL-17A, and reduce the development of RA-like disease in a humanized mouse model. These data suggest that T cells can be metabolically "re-engineered" ex vivo with exogenous mitochondria and that this mitochondria transfer approach confers anti-inflammatory properties that may reduce disease severity in RA and possibly other rheumatologic diseases. Increasing our understanding of how intercellular mitochondria transfer occurs may identify novel biological pathways that can be targeted therapeutically or harnessed to support cell engineering.

Keywords: CD4 T cells; mitochondria; rheumatoid arthritis.

Figure 1.. Exogenous mitochondria restore aspartate levels in CD4⁺ T cells to limit production of TNF-α and joint inflammation in rheumatoid arthritis-like disease.

(A) In the healthy joint, CD4⁺ T cells are rare and have normal mitochondrial metabolism that allows adequate concentrations of citric acid cycle intermediary metabolites, such as aspartate, to be produced. Aspartate suppresses production of proinflammatory cytokines, such as Tumor necrosis factor (TNF)-α. (B) CD4⁺ T cells from rheumatoid arthritis (RA) patients have reduced mitochondrial function and decreased concentrations of aspartate. The inhibitory effect of aspartate on TNF-α production is removed, leading to upregulated expression of this cytokine to drive inflammation and bone destruction in RA-afflicted joints. (C) Treating RA patient-derived T cells with healthy exogenous mitochondria restores mitochondrial metabolism in T cells, increases aspartate concentrations, and inhibits expression of TNF-α and other pro-inflammatory cytokines. Ex vivo mitochondria treatment of RA T cells attenuated joint inflammation and bone destruction in a humanized mouse model of RA-like disease, suggesting that mitochondria transfer could be utilized to “metabolically engineer” T cells for the treatment of rheumatologic diseases, such as RA.